Microbial Nitrogen Metabolism in Chloraminated Drinking Water Reservoirs

Abstract

<jats:title>Abstract</jats:title><jats:p>Nitrification is a common concern in chloraminated drinking water distribution systems. The addition of ammonia promotes the growth of nitrifying organisms, causing the depletion of chloramine residuals and resulting in operational problems for many drinking water utilities. Therefore, a comprehensive understanding of the microbially mediated processes behind nitrogen metabolism together with chemical water quality data, may allow water utilities to better address the undesirable effects caused by nitrification. In this study, a metagenomic approach was applied to characterise the microbial nitrogen metabolism within chloraminated drinking water reservoirs. Samples from two geographically separated but connected chloraminated reservoirs within the same drinking water distribution system (DWDS) were collected within a 2-year sampling campaign. Spatial changes in the nitrogen compounds (ammonium (NH<jats:sub>4</jats:sub><jats:sup>+</jats:sup>), nitrites (NO<jats:sub>2</jats:sub><jats:sup>−</jats:sup>) and nitrates (NO<jats:sub>3</jats:sub><jats:sup>−</jats:sup>)) across the DWDS were observed, where nitrate concentrations increased as the distance from the site of chloramination increased. The observed dominance of <jats:italic>Nitrosomonas</jats:italic> and <jats:italic>Nitrospira</jats:italic>-like bacteria, together with the changes in the concentration of nitrogen species, suggests that these bacteria play a significant role in contributing to varying stages of nitrification in both reservoirs. Functionally annotated protein sequences were mined for the genes associated with nitrogen metabolism and the community gene catalogue contained mostly genes involved in nitrification, nitrate and nitrite reduction and nitric oxide reduction. Furthermore, based on the construction of Metagenome Assembled Genomes (MAGs), a highly diverse assemblage of bacteria (i.e., predominately <jats:italic>Alpha</jats:italic>- and <jats:italic>Betaproteobacteria</jats:italic> in this study) was observed among the draft genomes. Specifically, 5 MAGs showed high coverage across all samples including two <jats:italic>Nitrosomonas, Nitrospira, Sphingomonas</jats:italic> and a <jats:italic>Rhizobiales</jats:italic>-like MAGs. The role of these MAGs in nitrogen metabolism revealed that the fate nitrate may be linked to changes in ammonia concentrations, that is, when ammonia concentrations are low, nitrate may be assimilated back to ammonia for growth. Alternatively, nitrate may be reduced to nitric oxide and potentially used in the regulation of biofilm formation. Therefore, this study provides insight into the genetic network behind microbially mediated nitrogen metabolism and together with the water chemistry data improves our understanding nitrification in chloraminated DWDSs.</jats:p>

Reproducible microbial community dynamics of two drinking water systems treating similar source waters

“…(ASV_6) in chloraminated distribution system samples from both systems. Here, the addition of chloramine as a secondary disinfectant has been shown to support the growth of nitrifying bacteria in DWDS 57 . The long residence time and associated lower disinfectant residual concentrations, together with the release of ammonia through disinfection decay results in increased abundance of nitrifiers and therefore potential nitrification 49 .…”

A 16S rRNA amplicon approach to the structural and functional diversity of bacterial communities associated with horse gram crop for drought mitigation and sustainable productivity

“…Applying slow‐release fertilizers at a greater depth increased the distribution and species richness of the rhizosphere microbiome and enhanced the relative abundance of nitrite reducers, such as Paenibacillus and Sphingomonas (Chen et al, 2022). Some genes that play major roles in nitrogen metabolism, such as ammonia oxidation ( amoCAB and hao ), assimilatory nitrate reduction ( nasA ), nitrite reduction ( nirA and nirB ), nitric oxide formation ( nirK ), nitric oxide reduction ( norCBQD ) and nitrite oxidation ( nxrAB ) (Potgieter et al, 2020), and the abundance of nifH genes of rhizobia in root nodules, are influenced by the low application of N fertilizers, which improve plant dry weight and increase functional metabolism, such as biological nitrogen fixation in plants (Li et al, 2019). The determination of functional traits and interactive signalling mechanisms in plant‐associated bacteria (PAB) based on purine metabolism helped to better understand the development of the consortium of plants under abiotic stress (Izaguirre‐Mayoral et al, 2018).…”

Pengaruh Usia Stabilisasi Tanah Gambut Melalui Bioaugmentasi Oleh Bakteri Pseudomonas Taiwanensis

“…Namun, keseluruhan variasi penambahan bakteri di masa pemeraman 14 hari dan 28 hari, mengalami penurunan kadar air yang konsisten. Berkurangnya kadar air diduga disebabkan oleh adanya aktivitas metabolisme bakteri yang memerlukan air (Potgieter et al, 2020). Selain itu, sampel tanah gambut tidak lagi memiliki mikropori sebagai akibat terurainya serat gambut, sehingga air mudah terevaporasi.…”